Option Strict On

Option Explicit On

​

Imports System

Imports System.Collections.Generic

Imports System.Linq

Public Module Module1

    Public Sub Main()

        'Write some values to a text file(example purposes only)

        IO.File.WriteAllLines("test.txt", "100,500,200,300,400".Split(","c))

        'Read the values

        Dim numbers() As Double = Array.ConvertAll(IO.File.ReadAllLines("test.txt"), Function(i) Convert.ToDouble(i))

        'Get each sum combination

        Dim combinations As List(Of Double()) = SumCombinations(1000, numbers)

        For Each dbl As Double() In combinations

            Console.WriteLine(String.Join(" + ", Array.ConvertAll(dbl, Function(d) d.ToString())))

        Next

    End Sub

    Private Function SumCombinations(ByVal target As Double, ByVal values() As Double) As List(Of Double())

        Dim sums, recursiveSums As New List(Of Double())

        Dim currentValues() As Double

​

        For index As Integer = 0 To values.Length - 2

            currentValues = values.Take(index).Skip(1).ToArray()

            If currentValues.Sum() = target Then

                sums.Add(currentValues)

            End If

            recursiveSums = SumCombinations(target, values.Skip(index).ToArray())

            sums.AddRange(recursiveSums.ToArray())

        Next

        Return sums

    End Function

End Module